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    <script>
    // ==(了解)
        /*
        1.倘若有一边的值为boolean,那么先将boolean-->number再比较
        2.倘若一边为字符串,一边为number,那么string-->number再比较
        3.null==undefined 
        4.NaN不能任何值计算,结果都为NaN
        NaN!=NaN-->true
        5.null和undefined比较之前不能将其转为其它类型
         */
         /* 
         0,"",NaN,undefined,null
          */
          console.log(Number(""));
          console.log(Number(null));
          console.log(0=="");
          console.log(NaN!=NaN)
          console.log(null===undefined);
          console.log(null==0);
    </script>
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